Devices of this kind are known and are described for example in the following patents: U.S. Pat. No. 4,312,336; U.S. Pat. No. Re. 31,809; DE 2718515; DE 3543042; DE 3701533; in said devices, the central body is connected to the first member by means of a spherical hinge and to the second member by means of another spherical hinge. Said spherical hinges can be locked in such a manner as to lock the relative position of the first member with respect to the second member.
However, said known devices entail some problems: first of all, the need to perform two detections, for example on two planes orientated at 90.degree. with respect to one another, entails difficult problems for the physician, since the position defined on one plane is unavoidably modified when an attempt is made to adjust the position on the second detection plane. This entails the problem of having to perform multiple successive checks between the two detection planes, so as to ensure that the position is correct. This problem is increased by the fact that the radiation useful for performing the checks, such as for example X rays, are harmful for the physician and for the patient.
Other devices of this kind are known and are described for example in the European patent No. 153546 and in the PCT patent no. VO 86/02822; in said devices, each screw is supported by a spherical hinge. Such devices have the same disadvantages as the above described known devices, and furthermore have a very limited articulation, so that if the holes for inserting the screws in the two bone fragments are not performed with great precision there is the risk of no longer being able to compose the fracture in the correct relative position of said two bone fragements.
Another device of this kind is also known and is described in the German patent application no. 2832283; in said device, the central body comprises a series of hinges. This device entails the same problems described in the preceding cases and in practice it has been found to be very complicated and difficult to use for the physician.